Question: Divide the following complex numbers: $\dfrac{7}{ e^{5\pi i / 3}}$ (The dividend is plotted in blue and the divisor in plotted in green. Your current answer will be plotted orange.)
Solution: Dividing complex numbers in polar forms can be done by dividing the radii and subtracting the angles. The first number ( $7$ ) has angle $0$ and radius 7. The second number ( $ e^{5\pi i / 3}$ ) has angle $\frac{5}{3}\pi$ and radius 1. The radius of the result will be $\frac{7}{1}$ , which is 7. The difference of the angles is $0 - \frac{5}{3}\pi = -\frac{5}{3}\pi$ The angle $-\frac{5}{3}\pi$ is negative. A complex number goes a full circle if its angle is increased by $2 \pi$ , so it goes back to itself. Because of that, angles of complex numbers are convenient to keep between $0$ and $2 \pi$ $-\frac{5}{3}\pi + 2 \pi = \frac{1}{3}\pi$ The radius of the result is $7$ and the angle of the result is $\frac{1}{3}\pi$.